Synchronous telegraphy



A. A. cLoKY l 1,742,899

SYNCHRONOUS TELEGRAPHY Jan. 7, .1930.

Filed Jan. 5. 1928 Patented Jaa. 7, 1930 f UNITED STATES PATENT ol-FICE ALLISON" A. CLOKEY, OF RUTHERCFORD, yNlif'W JERSEY, ASSIGNOR TO BELL TELEPHONE LABORATORIES, INCORPORATED, F NEW YORK, N. Y., A CORPORATION OF NEW YORK SYN CHRONOUS l TELEGRAPHY Application filed January 5, 1928. Serial No. 244,620.

This invention relates to synchronous communication systems and an object is to start auxiliary apparatus at an accurately definite time relative to the cycle of operation of main synchronous apparatus.

The invention relates more particularly to that type of synchronous telegraph system in which transmission is effected in only one direction at one time and the direction of transmission is periodically reversed by automatic switching means at each station. It has as an obj ect in such a system the starting of automatic switching means at separated stations substantially simultaneously.

In systems of this type it has been proposed to periodically reverse the direction o f transmission by means of an automatic switching mechanism at each station driven from the distributor shaft at that station through a friction clutch. In operation the switching mechanisms at all stations are initially set in their proper positions and restrained from rotating by a brake. ,After the distributors at all stations are properly synchronized the brakes restraining the switching mechanisms are released by transmitting a special impulse over lthe line from one of the stat-ions. This impulse operates a relay at each station ywhich releases the brake at that station, but, due to the ne required for an impulse to traverse a long cable and to the fact that two relays do not necessarily operate at the same speed, such an arrangement does not release the timing mechanisms at the different stations at exactly the same instant.

It has heretofore been proposed to start the timing mechanisms at the different stations with greater accuracy by controlling the starting relay at each station through a circuit involving segments on the synchronous distributor at that station so that the time of operation is controlled to a certain extent by the local synchronous distributor.

The present invention eliminates the necessity of a special electrical circuit involving segments lof the local distributors by substituting a mechanical tripping arrangement which is operated by the distributor brush drive shaft to release the timing mechanism.

5 In this way the time of starting the reversing timing mechanisms atdifferent stations may be controlled exactly and positively;

The drawing discloses schematically a simplex telegraph system adapted for transmission alternately inreach direction under the, control of automatic timing means for periodically reversing the direction of transmission. 1 represents la line conductor, which in this instance is shown as a submarine cable, extending between two stations A and B and ada ted to be connected to either receiving or sen ing equipment. at each station by means of automatic switching equipment. The apparatus atstation A has been shown in some detail but that at station B represented by a square, since the equipment at the two stations is identical. The receiving and sending equipment need not be described in detail; suffice it to say that the receiver, indicated by square R, and the transmitter, indicated by square T, comprise faces of a rotar synchronous distributor the brushes of which are driven from a shaft 3 by synchronous driving means SD. The latter comprises not only a constant speed motor but synchronousfcorrecting means operating to maintain the distributorl in synchronism with the distant station when the latter is transmitting. For a more complete description of suitable receiving, transmitting and synchronizing appara- -tus, the reader is referred tov Clokey Patent 1,601,941, October 5, 1926. I

The actual change from transmitting to receiving condition, and vice versa, at each station is made by a polar relay 2 which moves its armature from one contact to the other 'at intervals controlled by contacts 28, 7 and 9. These contacts are actuated by cams 'driven through a train of gears from the shaft 11. Shaft 11, in turn is driven from the main distributor shaft 3 through a friction clutch 14. Once the cams 6 and 8 at different stations are properly set they remain in phase as long as their respective distributor shafts 3 remain in phase but since if the motors SD are once shut down there is no provision for I restarting Vthem simultaneously, it is necessary, after they are started and synchronized, to stop the shaft 11 at each station, set the cams 6 and 8 to a predetermined position, and

then release the shafts 11 at the two stations simultaneousl ,or-at known intervals.

To release t e shafts 11. at each station this invention rovides a special startin mechanism l10, oi) which a full understan ing may bevreadily obtained by following through its operation in starting the timing mechanism.

Assume that the distributorv at the two stations are running in s nclironism but that the shaft 11 at each station is prevented from rotating by catch 12. The timing gear train at each `station is then set inthe predetermined position. This` may be done by manually pressing the catch 12 out of engagement with the cam 13 and allowing the friction clutch 14 to rotate'thc ca1ns,or means may be provided -for unmeshing the gears whereby7 each gear wheel can be set 1n the desired position and theny remeshed with its driving gear. -With the proper setting, cam

6 at station A is just 180' out of phase with the corresponding cam .at station B since when the latter station is switched from sending to receiving the former must be switched 16,-and snapped to the right (to the position shown in dotted lines) by spring 17 as cam 16 releases it. Each time the top of member 15 moves to the right-hand position it closes contacts 18 supplying current to relay. 19 but the relay cannot operate at this time because switch 20 is open. To release the timing mechanisms at the "two stations the operator at either station, in this case we will assume the operator at station A, closes switch 20. Thel first time member 15 moves to the right following the closure of this switch, current is supplied from battery 21 to contacts 18, switch 20, relay 19and contacts 22 to ground, operating relay 19, which is locked up by current supplied 'from battery overits own contact to ground throughY contacts 22. Current is simultaneously applied from the contact of relay 19, through relay 28 and inductance 24 to the cable, and thence through an inductance, two relays and a contact at the distant station corresponding respectively to those at station A. Inductance 24 is to prevent the usual telegraph signaling impulses from flowing in the starting relay circuit. Relay 23 at stationA thereupon operates and applies battery over its contacts to magnet 25, which attracts arm 26 avainst the end of member 15 so that when membber 15 moves to the left the catch on the end of arm 26 engages with it and when member 15 is subsequently snapped to the right by spring 17, when released by cams 16, the

with cam A13 and ermits the timin mechanism to be rotate bythe 'friction c utch t14. As the lower end of main catch 12 is pulled to the right the upper end moves to the left, where it is secured by the stop 27, and permanently o ens contacts 22, which breaks the flow o current through relay 19 and causes that relay to release. transmitted o ver the cable causes the re ease of shaft 11 at station B in the same manner as that outlined above for station A.

It shouldbe noted that between the time when member 15 closes contact 18 to apply an impulse to relays 19 and 23, and to the cable, and the time. when cam 13 is released by catch 12, the main distributor shaft 3 ,makes fpractically one Vcomplete revolution. Thus i the cable 1 isnot too long and has a speed* of propagation not too slow, the relays and magnets at station B, which correspond to relays 19 and 23 and magnet 25 at station A, may be operated before catch 12 at station A is released', since, when the distributors at the two stations are properly synchronized, members 15 are released simultaneously. Thus the timing mechanisms at The im ulse the two stations will be started at practically@` f the same instant and will operate to reverse the direction yof transmission at each station substantially simultaneously.

It may happen thatv the cable 1 is so long and has such a low speed of propagation that the distributor shafts will complete more than one revolution before the impulse transmitted to the cable atstation A reaches station B. In such a case the timing mechanism at station A would start at the 'end of one revolution but the timing mechanism at station B would not start until the end of the second or possibly a later revolution. Under such conditions a system of the type shown would not start the mechanisms at each end of the cable simultaneously but the mechanism at station B would always be started a definite number of revolutions of the disjtributor shaft later than the mechanism at station A and since this difference in starting time can be very exactly determined the timing mechanism at station B may be initially set'sulliciently ahead of that at station A to accurately compensate for the difference in starting time. v

Although the shaft 11 has been shown as l driven through a friction clutch and adapted to be restrained from turning by cam 13, it may in some instances be referable to couple the shaft 11 to its driving shaft through a clutch of the ty e which, when disengaged entirely releases t e shaft 11. Such a clutch may be released either mechanicall lor magnetically and is regarded as an equivalent of the friction clutch and stop cam system illustrated in the drawing. n

Although asystemv comprisingY only two terminal stations has been disclosed 1n the lll drawing, the invention is also applicable to a system in which there are more than two stations. For instance it is sometimes the practice to connect tWo sections of cable in series, and insert a repeating station between them for amplifying and reshaping the impulses received over one section for retransmission over the other section. In such a system it is necessary to reverse the receiving and transmitting apparatus at all three stations and the timing mechanism at all three stations may be released at definite intervals, i'n accordance withthis invention, in response to animpulse applied to the cable from one of the stations.

What is claimed is:

l. In a synchronous signaling system comprising a plurality of connected stations with synchronous driving means at all stations vrunning in phase, a mechanism to beset in motion at each station and means for starting each mechanism in response to a starting impulse from one of said stations characterized in this, that it comprises a tripping device actuated mechanically from the synchronous driving means at that station whereby the eX- act time of starting is determined.

2. In a synchronous communication system, a mechanism running at constant speed and periodically completing a cycle of motion, a second mechanism to be set in motion at a definite time in said cycle and vmeans for starting said second mechanism comprising manually controlled switching means, electromagnetic means operated under the joint control of said manually ,controlled switching means and said. first mechanism to begin the starting operation at said definite time, and tripping means mechanically operated from said first mechanism one cycle of time later to complete" the starting operation.

3. In a synchronous communication system a plurality of stations, a communication channel extending therebetween, synchronous distributing equipment at eachV station maintained in phase with that -at the other Vstations, secondary synchronous apparatus -at each station, and means for starting the secondary apparatus comprising a mechanism adapted to be set by an impulse received over said line and to be subsequently released by the synchronous distributing equipment at that station. y I

4. In a synchronous telegraph system comprising a plurality of connected stations with synchronous apparatus at each station maintained in phase with the synchronous apparatus at the other stations, a secondary synchronous switching means at each station, means for stopping said secondary means, and means for releasing said stopping means comprising alreleasing' memben under the whereby the exact time of releasin said stopping means is controlled by sai synchronous apparatus.

5. A telegraph conductor and a plurality of stations connected thereto, a distributor shaft at eachistation rotating at the same speed as, and in phase with, those at the other l stations, switching means at each station adapted to be effectively coupled to, or uncoupled from the synchronous distributor shaft at that station, and means for effectively coupling the switching means to the dis-l tributor shaft comprising a mechanism adapted to be set in response to an electric impulse and to be subsequently released by a mechanical tripping means operated from said distributor shaft.

6. In combination, a line conductor with a station at each end thereof, a synchronous distributor at each station, tripping means mechanically operated from the distributor at each station to trip at constant, definitely related time intervals, a device to be operated at each station at denitely related time intervals, electromagnetic means at each staelectromagnetic means being responsive to anelectric impulse received over said conductor, and switching means at sald statlons for applying an electric impulse simultaneously to the electromagnetic means at that station and tothe line conductor.

7. A system as defined in claim 5 further characterized in that'said switching means comprises contacts closed by said .mechanical tripping means whereby the impulse is applied to lthe electromagnetic means and to the conductor at a time substantially equal to thatof one cycle of operation of the tripping means before said tripping means trips.

8. In a synchronous telegraph system comrisino' two stations connected b a line conjoint control of an electromagnet and a cam driven from the *synchronous apparatus tion connected to said conductor for coupling said tripping device to said mechanism,'said 

